Surface treatment composition, method for producing surface treatment composition, surface treatment method, and method for producing semiconductor substrate

ABSTRACT

To provide a means capable of sufficiently removing organic residues present on the surface of a polishing object after polishing containing silicon oxide or polysilicon.A surface treatment composition contains a polymer having a constituent unit represented by Formula (1) below and water and is used for treating the surface of a polishing object after polishing,in which, in Formula (1) above, R1 is a hydrocarbon group having 1 to 5 carbon atoms and R2 is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms.

The present application is based upon and claims the benefit of priorityfrom Japanese Patent Application No. 2019-162883, filed Sep. 6, 2019,and Japanese Patent Application No. 2020-110739, filed Jun. 26, 2020.The entire contents of all of the above applications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a surface treatment composition, amethod for producing a surface treatment composition, a surfacetreatment method, and a method for producing a semiconductor substrate.

Description of the Related Art

In recent years, with multilayer-wiring on the surface of asemiconductor substrate, a so-called chemical mechanical polishing (CMP)art of polishing the semiconductor substrate for planarization has beenutilized in manufacturing a semiconductor device. The CMP is a methodfor planarizing the surface of a polishing object (object to bepolished), such as a semiconductor substrate, using a polishingcomposition (slurry) containing abrasives, such as silica, alumina, andceria, anticorrosives, surfactants, and the like. Examples of thepolishing object (object to be polished) include silicon, polysilicon, asilicon oxide film (silicon oxide), silicon nitride, wiring linescontaining a metal and the like, a plug, and the like.

On the semiconductor substrate surface after a CMP step, a large amountof impurities (defects) remain.

Examples of the impurities include organic matter, such as abrasives,metals, anticorrosives, and surfactants derived from a polishingcomposition used in the CMP, silicon containing materials and metalsgenerated by polishing silicon containing materials, metal wiring lines,plugs, and the like which are polishing objects, and further organicmatter, such as pad debris generated from various pads, for example.

When the semiconductor substrate surface is contaminated with theseimpurities, the electrical characteristics of the semiconductor areadversely affected, so that there is a possibility that the reliabilityof the semiconductor device decreases. Therefore, it is desirable tointroduce a cleaning step after the CMP step to remove these impuritiesfrom the semiconductor substrate surface.

As a cleaning liquid (cleaning composition) used for such a cleaningstep, one disclosed in PTL 1 is mentioned, for example. PTL 1 disclosesa slurry composition for chemical mechanical polishing containing water,polishing abrasives, and one or more types of water-soluble polymerscontaining a polyvinyl alcohol structural unit.

CITATION LIST Patent Literature

-   PTL 1: JP 2012-74678 A

SUMMARY OF THE INVENTION

In cleaning of a polishing object after polishing, a further defectreduction has been desired.

Herein, the present inventors have examined the relationship between thetype of the polishing object after polishing and the type of thedefects. As a result, the present inventors have found that organicresidues are likely to remain on the surface of the polishing objectafter polishing (for example, semiconductor substrate after polishing)containing silicon nitride, silicon oxide, or polysilicon and suchorganic residues may cause destruction of the semiconductor device.

The present invention has been made in view of the above-describedproblems. It is an object of the present invention to provide a meanscapable of sufficiently removing organic residues present on the surfaceof a polishing object after polishing containing silicon oxide orpolysilicon.

The present inventors have extensively advanced an examination in viewof the above-described problems. As a result, the present inventors havefound that organic residues present on the surface of a polishing objectafter polishing containing silicon oxide or polysilicon can besufficiently removed by the use of a surface treatment compositioncontaining a polymer having a constituent unit represented by Formula(1) below and water, and thus has accomplished the present invention.

In Formula (1) above, R¹ is a hydrocarbon group having 1 to 5 carbonatoms and R² is a hydrogen atom or a hydrocarbon group having 1 to 3carbon atoms.

The present invention provides a means capable of sufficiently removingorganic residues present on the surface of a polishing object afterpolishing containing silicon oxide or polysilicon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention is described. The present inventionis not limited only to the following embodiment.

In this specification, in the specific names of compounds, theindication “(meth)acryl” refers to “acryl” and “methacryl” and theindication “(meth)acrylate” refers to “acrylate” and “methacrylate”.

[Organic Residues]

In this specification, organic residues indicate components containingorganic matter, such as organic low molecular weight compounds and highmolecular weight compounds, organic salts, and the like amongcontaminants adhering to the surface of a polishing object afterpolishing.

Examples of the organic residues adhering to a cleaning object includepad debris generated from a pad used in a polishing step or a rinsepolishing step which may be optionally provided described later,components derived from additives contained in a polishing compositionused in the polishing step or a rinse polishing composition used in therinse polishing step, and the like, for example.

The organic residues and the other contaminants are greatly different incolor and shape. Therefore, it can be visually determined by SEMobservation whether the contaminants are the organic residues. Asnecessary, the determination may also be performed by ultimate analysisby means of energy dispersive X-ray spectroscopy (EDX).

[Polishing Object after Polishing]

In this specification, the polishing object after polishing means apolishing object after being polished in the polishing step. Thepolishing step is not particularly limited and is preferably a CMP step.

A surface treatment composition according to one aspect of the presentinvention is preferably used for reducing the organic residues remainingon the surface of a polishing object after polishing (hereinafter alsosimply referred to as “cleaning object”) containing silicon nitride(hereinafter also simply referred to as “SiN”), silicon oxide, orpolysilicon (hereinafter also simply referred to as “Poly-Si”). Examplesof the polishing object after polishing containing silicon oxideinclude, for example, a TEOS type silicon oxide surface (hereinafteralso simply referred to as “TEOS”) generated using tetraethylorthosilicicate as a precursor, an HDP film, a USG film, a PSG film, aBPSG film, an RTO film, and the like.

The polishing object after polishing is preferably a semiconductorsubstrate after polishing and is more preferably a semiconductorsubstrate after the CMP. This is because particularly the organicresidues may cause destruction of a semiconductor device, and therefore,when the polishing object after polishing is a semiconductor substrateafter polishing, a cleaning step of the semiconductor substrate isrequired to be a step capable of removing the organic residues as muchas possible.

Examples of the polishing object after polishing containing siliconnitride, silicon oxide, or polysilicon include, but are not particularlylimited to, a polishing object after polishing containing a siliconnitride simple substance, a silicon oxide simple substance, and apolysilicon simple substance, a polishing object after polishing in astate in which materials other than silicon nitride, silicon oxide, andpolysilicon are exposed to the surface in addition to silicon nitride,silicon oxide, or polysilicon, and the like. Herein, examples of theformer include, for example, a silicon nitride substrate, a siliconoxide substrate, or a polysilicon substrate which is a conductorsubstrate. As the latter, the materials other than silicon nitride,silicon oxide, or polysilicon are not particularly limited and tungstenand the like are mentioned, for example. Specific examples of suchpolishing object after polishing include a semiconductor substrate afterpolishing having a structure in which a silicon nitride film, a siliconoxide film, or a polysilicon film is formed on tungsten, a semiconductorsubstrate after polishing having a structure in which a tungstenportion, a silicon nitride film, a silicon oxide film, and a polysiliconfilm are all exposed, and the like.

Herein, the polishing object after polishing according to one aspect ofthe present invention preferably contains polysilicon from the viewpointof the effects exhibited by the present invention.

[Surface Treatment Composition]

One aspect of the present invention is a surface treatment compositioncontaining a polymer having a constituent unit represented by Formula(1) below and water, and used for treating the surface of the polishingobject after polishing.

In Formula (1) above, R¹ is a hydrocarbon group having 1 to 5 carbonatoms and R² is a hydrogen atom or a hydrocarbon group having 1 to 3carbon atoms.

The surface treatment composition according to one aspect of the presentinvention is particularly preferably used as an organic residuereduction agent for selectively removing the organic residue in asurface treatment step.

The present inventors estimate a mechanism that the above-describedproblems are solved by the present invention as follows. The surfacetreatment composition has a function of removing the contaminants on thesurface of the polishing object after polishing or facilitating theremoval as a result of a chemical interaction between each componentcontained in the surface treatment composition, and the surface of thepolishing object after polishing and the contaminants.

The polymer having the constituent unit represented by Formula (1) canchange a hydrophobic wafer surface to a hydrophilic wafer surface byphysically adsorbing to the hydrophobic wafer surface. The organicresidues adhering onto the wafer temporarily float during treatment, andthereafter the polymer adsorbs to the wafer. As a result, a layer formedof the polymer functions as a re-adhesion prevention layer of theorganic residues, and thus the organic residues can be easily removedfrom the wafer.

The above-described mechanism is based on a presumption, and thuscorrection or in correction thereof does not affect the technical scopeof the present invention.

Hereinafter, each component contained in the surface treatmentcomposition is described.

[Polymer Having Constituent Unit Represented by Formula (1)]

As the hydrocarbon group having 1 to 5 carbon atoms represented by R¹ inFormula (1) above, alkyl groups, such as a methyl group, an ethyl group,and a propyl group; alkenyl groups, such as an ethenyl group and apropenyl group; alkynyl groups, such as an ethynyl group and a propynylgroup, cycloalkyl groups, such as a cyclopentyl group; and the like canbe mentioned. Among the above, the alkyl groups and the alkynyl groupsare preferable and hydrocarbon groups having 1 to 3 carbon atoms arealso preferable. As R¹, the methyl group, the ethyl group, and theethenyl group (vinyl group) are more preferable and the methyl group andthe ethyl group are still more preferable.

As the hydrocarbon groups having 1 to 3 carbon atoms represented by R²in Formula (1) above, those having 1 to 3 carbon atoms among thoseillustrated as the hydrocarbon groups having 1 to 5 carbon atomsrepresented by R¹ can be mentioned. As R², a hydrogen atom and a methylgroup are preferable.

As unsaturated monomers giving the above-described constituent units,N-vinylacetamide, N-vinylpropionamide, N-vinylbutylamide, and the likecan be mentioned and the N-vinylacetamide and the N-vinylpropionamideare preferable. The unsaturated monomers above can be used alone or as amixture of two or more types thereof.

The weight average molecular weight (Mw) of the polymer is usually30,000 or more and 1,000,000 or less, preferably 50,000 or more and900,000 or less, and more preferably 50,000 or more and 100,000 or less.By setting the weight average molecular weight (Mw) of the polymerwithin the range above, the organic residues on the surface of thepolishing object after polishing can be more effectively reduced.

The lower limit of the content (total amount in a case of two or moretypes) of the polymer having the constituent unit represented by Formula(1) is not particularly limited and is preferably 0.02 mass % or morebased on the total amount of the surface treatment composition. When thecontent is 0.02 mass % or more, the organic residues on the surface ofthe polishing object after polishing can be more effectively reduced.

From a similar viewpoint, a lower limit value of the content of thepolymer having the constituent unit represented by Formula (1) is morepreferably 0.03 mass % or more and still more preferably 0.05 mass % ormore based on the total amount of the surface treatment composition. Onthe other hand, an upper limit value of the content of the polymerhaving the constituent unit represented by Formula (1) is preferably 1mass % or less based on the total amount of the surface treatmentcomposition. When the content is 1 mass % or less, the removal of thepolymer having the constituent unit represented by Formula (1) itselfafter surface treatment is facilitated. From a similar viewpoint, theupper limit value of the content of the polymer having the constituentunit represented by Formula (1) is more preferably 0.7 mass % or lessand still more preferably 0.5 mass % or less based on the total amountof the surface treatment composition.

The content of the constituent unit in the polymer is preferably 30 mol% or more and 100 mol % or less, more preferably 50 mol % or more and100 mol % or less, and still more preferably 70 mol % or more and 100mol % or less. By setting the content of the constituent unit within therange above, the organic residues on the surface of the polishing objectafter polishing can be more effectively reduced.

[Water-Soluble Polymer Having Constituent Unit Derived from Glycerol]

The surface treatment composition according to one aspect of the presentinvention may also contain a water-soluble polymer having a constituentunit derived from glycerol.

Preferable examples of the water-soluble polymer having the constituentunit derived from glycerol include at least one type selected from thegroup consisting of polyglycerol (see Formula (2) below), alkyl (C10 to14) ester of polyglycerol, polyglycerol alkyl (C10 to 14) ether,ethylene oxide-modified polyglycerol, sulfonic acid-modifiedpolyglycerol (for example, see Formulae (3) and (4) below), andphosphonic acid-modified polyglycerol (for example, see Formulae (5) and(6) below).

m and n in Formulae (2) to (6) above each independently represent thenumber of repeating units. M in Formulae (3) to (6) above eachindependently represent a hydrogen atom, Na, K, or NH₄ ⁺.

A plurality of Ms in Formulae (3) to (6) above may be the same or may bedifferent from each other. For example, n pieces of Ms in Formula (3)above may be all Na or may be a combination of two or more types of ahydrogen atom, Na, K, and NH₄ ⁺. For example, m pieces of Ms in Formula(4) above may be all Na or may be a combination of two or more types ofa hydrogen atom, Na, K, and NH₄ ⁺.

The water-soluble polymers having the constituent unit derived fromglycerol can be used alone or in combination of two or more typesthereof.

The content (concentration) (total amount in a case of two or moretypes) of the water-soluble polymer having the constituent unit derivedfrom glycerol is not particularly limited and is preferably 0.02 mass %or more based on the total amount of the surface treatment composition.When the content of the water-soluble polymer having the constituentunit derived from glycerol is 0.02 mass % or more, the effects of thepresent invention are improved.

From a similar viewpoint, the content (concentration) of thewater-soluble polymer having the constituent unit derived from glycerolis more preferably 0.03 mass % or more and still more preferably 0.05mass % or more based on the total amount of the surface treatmentcomposition. The content (concentration) of the water-soluble polymerhaving the constituent unit derived from glycerol is preferably 1 mass %or less based on the total amount of the surface treatment composition.When the content (concentration) of the water-soluble polymer having theconstituent unit derived from glycerol is 1 mass % or less, the removalof the water-soluble polymer having the constituent unit derived fromglycerol itself after surface treatment is facilitated. From a similarviewpoint, the content (concentration) of the water-soluble polymerhaving the constituent unit derived from glycerol is more preferably 0.7mass % or less and still more preferably 0.5 mass % or less based on thetotal amount of the surface treatment composition.

The weight average molecular weight (Mw) of the water-soluble polymerhaving the constituent unit derived from glycerol is preferably 1,000 ormore. When the weight average molecular weight is 1,000 or more, thecontaminant removal effect is further improved. This is presumed to bebecause the covering property when the water-soluble polymer having theconstituent unit derived from glycerol covers the cleaning object or thecontaminants is further improved, so that a removal action of thecontaminants from the cleaning object surface or a re-adhesionsuppressing action of the contaminants to the cleaning object surface isfurther improved. From a similar viewpoint, the weight average molecularweight is more preferably 3,000 or more and still more preferably 8,000or more. An upper limit value of the weight average molecular weight ofthe water-soluble polymer having the constituent unit derived fromglycerol is not particularly limited and is preferably 1,000,000 orless, more preferably 100,000 or less, and still more preferably 50,000or less. The weight average molecular weight can be determined in termsof polyethylene glycol using a GPC apparatus (manufactured by ShimadzuCorporation, Model type: Prominence+ELSD detector (ELSD-LTII)) or thelike by gel permeation chromatography (GPC) and specifically can bemeasured by a method described in Examples.

As the water-soluble polymer having the constituent unit derived fromglycerol, commercially-available items may be used or synthetic productsmay be used. A production method in a case of performing synthesis isnot particularly limited and known polymerization methods are usable.

[Acid]

The surface treatment composition according to one aspect of the presentinvention may also contain acids. In this specification, an ionicdispersant described below is dealt with as an acid different from acidsas additives described herein. The acids are added for the purpose ofmainly adjusting the pH of the surface treatment composition.

It is presumed that the acids play a role of charging the surface of thepolishing object after polishing or the contaminant surfaces withpositive charges when the polishing object after polishing containssilicon nitride, silicon oxide, or polysilicon. Therefore, when thesurface treatment composition is used to contaminants or a cleaningobject having a property capable of positively charging the surfacetreatment composition, an electrostatic repulsion effect is furtherpromoted by adding the acids, so that the contaminant removal effect bythe surface treatment composition is further improved.

As the acids, either inorganic acids or organic acids may be used.Examples of the inorganic acids include, but are not particularlylimited to, sulfuric acid, nitric acid, boric acid, carbonic acid,hypophosphorous acid, phosphorous acid, phosphoric acid, and the like,for example. Examples of the organic acids include, but are notparticularly limited to, carboxylic acids, such as formic acid, aceticacid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid,n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid,4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid,n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid,salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid,malic acid, tartaric acid, citric acid, and lactic acid, methanesulfonicacid, ethanesulfonic acid, isethionic acid, and the like.

Among the above, maleic acid or nitric acid is more preferable from theviewpoint that an effect of charging the surface of the polishing objectafter polishing or the contaminant surfaces with positive charges isfurther improved and the removability of the contaminants is increased.

The acids can be used alone or in combination of two or more typesthereof.

The content of the acids is preferably 0.01 mass % or more based on thetotal amount of the surface treatment composition. When the content ofthe acids is 0.01 mass % or more, the contaminant removal effect isfurther improved. This is presumed to be because the effect of chargingthe surface of the polishing object after polishing or the contaminantsurfaces with positive charges is further improved. From a similarviewpoint, the content of the acids is preferably 0.02 mass % or moreand more preferably 0.03 mass % or more based on the total amount of thesurface treatment composition. The content of the acids is preferably 5mass % or less based on the total amount of the surface treatmentcomposition. The content is preferable from the viewpoint that the costis reduced when the content of the acids is 5 mass % or less. From asimilar viewpoint, the content of the acids is more preferably 3 mass %or less and still more preferably 1 mass % or less based on the totalamount of the surface treatment composition.

[Dispersion Medium]

The surface treatment composition according to one aspect of the presentinvention essentially contains water as a dispersion medium (solvent).The dispersion medium has a function of dispersing or dissolving eachcomponent. The dispersion medium is more preferably only water.

Alternatively, the dispersion medium may be a mixed solvent of water andorganic solvents for the dispersion or the dissolution of eachcomponent. In this case, examples of the organic solvents to be usedinclude acetone, acetonitrile, ethanol, methanol, isopropanol, glycerol,ethylene glycol, propylene glycol, and the like which are organicsolvents mixed with water. Alternatively, these organic solvents may beused without being mixed with water and may be mixed with water afterdispersing or dissolving each component. These organic solvents can beused alone or in combination of two or more types thereof.

Water is preferably water free from impurities as much as possible fromthe viewpoint of contamination of the cleaning object or blocking ofactions of other components. For example, water having a total contentof transition metal ions of 100 ppb or less is preferable. Herein, thepurity of water can be increased by an operation, such as the removal ofimpurity ions using an ion-exchange resin, the removal of contaminantswith a filter, or distillation, for example. Specifically, as water,deionized water (ion exchange water), pure water, ultrapure water,distilled water, and the like are preferably used, for example.

[pH]

The pH of the surface treatment composition according to one aspect ofthe present invention may exceed 5 but is preferably 5 or less. In thecase where the pH is 5 or less, when the surface treatment compositionis used for the contaminants or the cleaning object having a propertycapable of positively charging the surface treatment composition, thecleaning object surface or the contaminant surfaces can be morecertainly charged with positive charges and a higher contaminant removaleffect can be obtained by electrostatic repulsion. When the pH exceeds5, the contaminant removal effect is hard to obtain under specificconditions (for example, silicon nitride substrate after polishing asillustrated in Example 10 described later). The pH is more preferably 4or less, still more preferably 3 or less, and yet still more preferablyless than 3 (for example, 2.5). The pH of the surface treatmentcomposition is preferably 1 or more. When the pH is 1 or more, the costcan be further reduced.

A pH value of the surface treatment composition can be confirmed with apH meter (manufactured by HORIBA, LTD., Product Name: LAQUA (RegisteredTrademark)).

When adjusting the pH value, components other than the surface treatmentcomposition according to one aspect of the present invention may serveas a cause of contaminants, and therefore are not preferably added asmuch as possible. Therefore, the surface treatment composition ispreferably prepared only from the water-soluble polymer having theconstituent unit derived from glycerol, acids, water, and the ionicdispersants added as necessary. However, when it is difficult to obtaina desired pH only by these substances, the pH may be adjusted usingother additives, such as alkali, which may be optionally added withinthe range where the effects of the present invention are not impaired.

[Ionic Dispersant]

The surface treatment composition according to one aspect of the presentinvention preferably further contains the ionic dispersant. The ionicdispersant contributes to the removal of the contaminants by the surfacetreatment composition. Hence, the surface treatment compositioncontaining the ionic dispersant can sufficiently remove the contaminants(impurities including the organic residues and the like) remaining onthe surface of the polishing object after polishing in the surfacetreatment (cleaning or the like) of the polishing object afterpolishing.

Examples of the ionic dispersant include high molecular weight compoundshaving a sulfonic acid (salt) group; high molecular weight compoundshaving a phosphoric acid (salt) group; high molecular weight compoundshaving a phosphonic acid (salt) group; high molecular weight compoundshaving a carboxylic acid (salt) group; water-soluble polymers containingnitrogen atoms, such as polyvinyl pyrrolidone (PVP), polyvinyl imidazole(PVI), polyvinyl carbazole, polyvinyl caprolactam, polyvinyl piperidine,and polyacryloyl morpholine (PACMO); polyvinyl alcohol (PVA);hydroxyethylcellulose (HEC); and the like.

Among the above, the high molecular weight compounds having a sulfonicacid (salt) group are preferable. Hereinafter, the high molecular weightcompounds having a sulfonic acid (salt) group are described.

<High Molecular Weight Compounds Having Sulfonic Acid (Salt) Group>

It is preferable in the surface treatment composition according to oneaspect of the present invention that the ionic dispersant is the highmolecular weight compound having a sulfonic acid (salt) group. The highmolecular weight compound having a sulfonic acid (salt) group(hereinafter also simply referred to as “sulfonic acid group-containingpolymer” in this specification) is likely to contribute to the removalof the contaminants by the surface treatment composition. Hence, thesurface treatment composition containing the sulfonic acidgroup-containing polymer described above has an effect that thecontaminants (impurities including the organic residues and the like)remaining on the surface of the polishing object after polishing aremore easily removed in the surface treatment (cleaning or the like) ofthe polishing object after polishing.

The sulfonic acid group-containing polymer can form micelles due toaffinity between a portion other than the sulfonic acid (salt) group(i.e., polymer chain portion of the sulfonic acid group-containingpolymer) and the contaminants (particularly hydrophobic components).Hence, it is considered that, due to the micelles being dissolved ordispersed in the surface treatment composition, the contaminants whichare the hydrophobic components are also effectively removed.

Under an acidic condition, when the surface of the polishing objectafter polishing is cationic, the sulfonic acid group-containing polymeris likely to adsorb to the surface of the polishing object afterpolishing by the an ionizing of the sulfonic acid group. As a result, itis considered that the sulfonic acid group-containing polymer covers thesurface of the polishing object after polishing. On the other hand, thesulfonic acid group of the sulfonic acid group-containing polymer islikely to adsorb to the remaining contaminants (particularly those whichare easily cationized), and therefore the contaminant surfaces areanionized. Hence, the contaminants having surfaces which have becomeanionic and the anionized sulfonic acid group of the sulfonic acidgroup-containing polymer adsorbing to the surface of the polishingobject after polishing electrostatically repulse each other. When thecontaminants are anionic, the contaminants themselves and the anionizedsulfonic acid group present on the polishing object after polishingelectrostatically repulse each other. Therefore, it is considered thatthe contaminants can be effectively removed by utilizing suchelectrostatic repulsion.

Furthermore, when the polishing object after polishing is hard to becharged, it is presumed that the contaminants are removed by a mechanismdifferent from the mechanism described above. First, it is consideredthat the contaminants (particularly hydrophobic components) are in astate of being likely to adhere to the polishing object after polishingwhich is hydrophobic by a hydrophobic interaction. Herein, the polymerchain portion (hydrophobic structure part) of the sulfonic acidgroup-containing polymer is directed to the surface side of thepolishing object after polishing due to the hydrophobicity thereof.Whereas, the anionized sulfonic acid group and the like which arehydrophilic structural parts are directed to the side opposite to thesurface side of the polishing object after polishing. Thus, it ispresumed that the surface of the polishing object after polishing iscovered with the anionized sulfonic acid group to become hydrophilic. Asa result, it is considered that the hydrophobic interaction is hard tooccur between the contaminants (particularly hydrophobic components) andthe polishing object after polishing, and thus the adhesion of thecontaminants is suppressed.

Then, the polymer having the constituent unit represented by Formula (1)above adsorbing to the surface of the polishing object after polishing,the water-soluble polymer having the constituent unit derived fromglycerol, and the sulfonic acid group-containing polymer are easilyremoved by further performing water cleaning or the like.

In this specification, the “sulfonic acid (salt) group” indicates asulfonic acid group (—SO₃H) or a salt group thereof (—SO₃M²; herein, M²is an organic or inorganic cation).

The sulfonic acid group-containing polymer is not particularly limitedin so far as it has a plurality of sulfonic acid (salt) groups and knowncompounds are usable. Examples of the sulfonic acid group-containingpolymer include high molecular weight compounds obtained by sulfonatinga high molecular weight compound serving as a base, high molecularweight compounds obtained by (co)polymerizing a monomer having asulfonic acid (salt) group, and the like.

More specifically, sulfonic acid (salt) group-containing polystyrenes,such as sulfonic acid (salt) group-containing polyvinyl alcohols(sulfonic acid-modified polyvinyl alcohols), polystyrene sulfonate, andsodium polystyrene sulfonate, sulfonic acid (salt) group-containingpolyvinyl acetates (sulfonic acid-modified polyvinyl acetates), sulfonicacid (salt) group-containing polyesters, copolymers of (meth)acrylicgroup-containing monomer-sulfonic acid (salt) group-containing monomer,such as copolymers of (meth)acrylic acid-sulfonic acid (salt)group-containing monomer, and the like are mentioned. In thisspecification, in the specific names of compounds, the indication“(meth)acryl” refers to “acryl” and “methacryl” and the indication“(meth)acrylate” refers to “acrylate” and “methacrylate”. Theabove-described sulfonic acid group-containing polymers can be usedalone or in combination of two or more types thereof. At least one partof the sulfonic acid group possessed by the polymers may have a form ofa salt. Examples of the salts include alkali metal salts, such as sodiumsalts and potassium salts, salts of Group II elements, such as calciumsalts and magnesium salts, amine salts, ammonium salts, and the like. Inparticular, when the polishing object after polishing is a semiconductorsubstrate after the CMP step, ammonium salts are preferable from theviewpoint of removing metals on the substrate surface as much aspossible.

When the sulfonic acid group-containing polymer is sulfonic acidgroup-containing polyvinyl alcohol, the degree of saponification ispreferably 80% or more and more preferably 85% or more (upper limit of100%) from the viewpoint of solubility.

In the present invention, the weight average molecular weight of thesulfonic acid group-containing polymer is preferably 1,000 or more. Whenthe weight average molecular weight is 1,000 or more, the contaminantremoval effect is further increased. This is presumed to be because thecovering property in covering the polishing object after polishing orthe contaminants is further improved, so that the removal action of thecontaminants from the cleaning object surface or the re-adhesionsuppressing action of the organic residues to the surface of thepolishing object after polishing is further improved. From a similarviewpoint, the weight average molecular weight is more preferably 2,000or more and still more preferably 8,000 or more.

The weight average molecular weight of the sulfonic acidgroup-containing polymer is preferably 100,000 or less. When the weightaverage molecular weight is 100,000 or less, the contaminant removaleffect is further increased. This is presumed to be because theremovability of the sulfonic acid group-containing polymer after thecleaning step is further improved. From a similar viewpoint, the weightaverage molecular weight is more preferably 50,000 or less and stillmore preferably 40,000 or less.

The weight average molecular weight can be measured by gel permeationchromatography (GPC) and specifically can be measured by a methoddescribed in Examples.

As the sulfonic acid group-containing polymer, commercially-availableitems may be used, and for example, GOHSENX (Registered Trademark)L-3226 and GOHSENX (Registered Trademark) CKS-50 manufactured by NipponSynthetic Chemical Industry Co., Ltd., Aron (Registered Trademark)A-6012, A-6016A, and A-6020 manufactured by Toagosei Co., Ltd., PolyNaSS(Registered Trademark) PS-1 manufactured by Tosoh Organic Chemical Co.,Ltd., and the like are usable.

The content (concentration) of the sulfonic acid group-containingpolymer is preferably 0.001 mass % or more based on the total amount ofthe surface treatment composition. When the content of the sulfonic acidgroup-containing polymer is 0.001 mass % or more, the contaminantremoval effect is further improved. This is presumed to be because, whenthe sulfonic acid group-containing polymer covers the polishing objectafter polishing and the contaminants, the polishing object afterpolishing and the contaminants are covered in larger areas. Thus,particularly the contaminants easily form micelles, and therefore thecontaminant removal effect by the dissolution/dispersion of the micellesis improved. Moreover, it is presumed to be because the electrostaticadsorption or the repulsion effect can be more strongly revealed due toan increase in the number of the sulfonic acid (salt) groups. From asimilar viewpoint, the content (concentration) of the sulfonic acidgroup-containing polymer is more preferably 0.003 mass % or more andstill more preferably 0.005 mass % or more based on the total amount ofthe surface treatment composition. The content (concentration) of thesulfonic acid group-containing polymer is preferably 0.5 mass % or lessbased on the total amount of the surface treatment composition. When thecontent (concentration) of the sulfonic acid group-containing polymer is0.5 mass % or less, the contaminant removal effect is further increased.This is presumed to be because the removability of the sulfonic acidgroup-containing polymer itself after the cleaning step is improved.From a similar viewpoint, the content of the sulfonic acidgroup-containing polymer is more preferably 0.2 mass % or less, stillmore preferably 0.1 mass % or less, and particularly preferably 0.05mass % or less based on the total amount of the surface treatmentcomposition.

In this specification, the “high molecular weight compound” refers to acompound having a weight average molecular weight of 1,000 or more.

[Other Additives]

The surface treatment composition according to one aspect of the presentinvention may further contain other additives in any proportion asnecessary within the range where the effects of the present inventionare not impaired. However, components other than the essentialcomponents of the surface treatment composition according to one aspectof the present invention may be a cause of the contaminants, and thusthe addition is desirably minimized. Thus, it is preferable that thecomponents other than the essential components are added in as smallamounts as possible and it is more preferable that such components arenot contained. Examples of other additives include, for example,abrasives, alkali, antiseptic agents, dissolved gases, reducing agents,oxidants, alkanolamines, and the like. Among the above, the surfacetreatment composition is preferably substantially free from abrasivesfor a further improvement of the contaminant removal effect. Herein, thedescription “substantially free from abrasives” refers to a case wherethe content of the abrasives based on the entire surface treatmentcomposition is 0.01 mass % or less.

As the number of the contaminants (organic residues), a value measuredby a method described in Examples after performing the surface treatmentby a method described in Examples is adopted.

[Method for Producing Surface Treatment Composition]

A method for producing the above-described surface treatment compositionis not particularly limited. For example, the surface treatmentcomposition can be produced by mixing the polymer having the constituentunit represented by Formula (1) above and water. More specifically,another aspect of the present invention further provides a method forproducing the above-described surface treatment composition includingmixing the polymer having the constituent unit represented by Formula(1) above and water. The types, the addition amounts, and the like ofthe polymer having the constituent unit represented by Formula (1) aboveare as described above. Furthermore, in the method for producing thesurface treatment composition according to one aspect of the presentinvention, the ionic dispersant, the water-soluble polymer having theconstituent unit derived from glycerol (glycerol-based water-solublepolymer), other additives, dispersion media other than water, and thelike may be further mixed as necessary. The types, the addition amounts,and the like thereof are as described above.

The order of addition and methods of addition of the components aboveare not particularly limited. The materials above may be added at onceor separately or in stages or continuously. Moreover, mixing methods arealso not particularly limited and known methods are usable. Preferably,the method for producing the above-described surface treatmentcomposition includes successively adding the water-soluble polymerhaving the constituent unit derived from glycerol, acids, water, and theionic dispersant added as necessary, followed by stirring in water. Inaddition thereto, the method for producing the above-described surfacetreatment composition may further include measuring the pH of thesurface treatment composition, and then adjusting the pH to 5 or less.

[Surface Treatment Method]

Another aspect of the present invention is a surface treatment methodincluding surface-treating the polishing object after polishing usingthe above-described surface treatment composition. In thisspecification, the surface treatment method refers to a method includingreducing the contaminants on the surface of the polishing object afterpolishing and is a method including performing cleaning in a broadsense.

The surface treatment method according to one aspect of the presentinvention can sufficiently remove the contaminants remaining on thesurface of a polishing object after polishing. More specifically,another aspect of the present invention provides a method for reducingthe contaminants on the surface of the polishing object after polishingincluding surface-treating the polishing object after polishing usingthe above-described surface treatment composition.

The surface treatment method according to one aspect of the presentinvention is performed by a method including bringing the surfacetreatment composition according to the present invention into directcontact with the polishing object after polishing.

Examples of the surface treatment method mainly include (I) a method byrinse polishing treatment and (II) a method by cleaning treatment. Morespecifically, the surface treatment according to one aspect of thepresent invention is preferably performed by rinse polishing orcleaning. The rinse polishing treatment and the cleaning treatment arecarried out to remove the contaminants (particles, metal contamination,organic residues, pad debris, and the like) on the surface of thepolishing object after polishing, thereby obtaining a clean surface. Theabove methods (I) and (II) are described below.

(I) Rinse Polishing Treatment

The surface treatment composition according to the present invention issuitably used in the rinse polishing treatment. The rinse polishingtreatment is performed on a polishing platen to which a polishing pad isattached for the purpose of removing the contaminants on the surface ofthe polishing object after the polishing object has been subjected tofinal polishing. At this time, the rinse polishing treatment isperformed by bringing the surface treatment composition according to thepresent invention into direct contact with the polishing object afterpolishing. As a result, the contaminants on the surface of the polishingobject after polishing are removed by frictional force (physical action)by the polishing pad and chemical action by the surface treatmentcomposition. Among the contaminants, particularly the particles and theorganic residues are easily removed by the physical action. Therefore,in the rinse polishing treatment, the particles and the organic residuescan be effectively removed by utilizing the friction with the polishingpad on the polishing platen.

Specifically, the rinse polishing treatment can be performed byinstalling the surface of the polishing object after polishing after thepolishing step on the polishing platen of a polishing device to bringthe polishing pad and the semiconductor substrate after polishing intocontact with each other, and then causing the polishing object afterpolishing and the polishing pad to slide relative to each other whilesupplying the surface treatment composition (rinse polishingcomposition) to a contact region of the polishing pad and thesemiconductor substrate after polishing.

The rinse polishing treatment can also be performed whichever a one-sidepolishing device or a double-side polishing device is used. Thepolishing device preferably has a discharge nozzle for the rinsepolishing composition in addition to a discharge nozzle for a polishingcomposition. The operating conditions in the rinse polishing treatmentof the polishing device are not particularly limited and can be set asappropriate by a person skilled in the art.

(II) Cleaning Treatment

The surface treatment composition according to the present invention issuitably used in the cleaning treatment. The cleaning treatment isperformed for the purpose of removing the contaminants on the surface ofthe polishing object after the polishing object has been subjected tofinal polishing or to the above-described rinse polishing treatment. Thecleaning treatment and the above-described rinse polishing treatment areclassified according to the place where the treatment is performed. Thecleaning treatment is surface treatment performed after removing thepolishing object after polishing from the polishing platen. Also in thecleaning treatment, the contaminants on the surface of the polishingobject can be removed by bringing the surface treatment compositionaccording to the present invention into direct contact with thepolishing object after polishing.

Examples of methods for performing the cleaning treatment include (i) amethod including bringing a cleaning brush into contact with one side orboth sides of the polishing object after polishing in a state of holdingthe polishing object after polishing, and then rubbing the surface of acleaning object with the cleaning brush while supplying the surfacetreatment composition to a contact region of the cleaning blush and thepolishing object after polishing; (ii) a method including immersing thepolishing object after polishing in the surface treatment composition,followed by performing ultrasonic treatment or stirring (dip method);and the like. In such methods, the contaminants on the surface of thepolishing object are removed by the frictional force by the cleaningbrush or the mechanical force generated by the ultrasonic treatment orthe stirring and the chemical action by the surface treatmentcomposition.

In the method (i) above, examples of the method for bringing the surfacetreatment composition (cleaning composition) into contact with thepolishing object after polishing include, but are not particularlylimited to, a spin method including rotating the polishing object afterpolishing at a high speed while pouring the surface treatmentcomposition onto the polishing object after polishing from a nozzle, aspray method including cleaning the polishing object after polishing byspraying the surface treatment composition thereto, and the like.

From a point that more efficient contamination removal can be performedin a short time, the spin method or the spray method is preferablyadopted as the cleaning treatment and the spin method is morepreferable.

Examples of devices for performing such cleaning treatment include abatch cleaning device in which a plurality of polishing objects afterpolishing placed in a cassette are simultaneously surface-treated, asingle-wafer cleaning device in which one polishing object afterpolishing is attached to a holder and surface-treated, and the like.From the viewpoint of reducing the cleaning time, for example, a methodusing the single-wafer cleaning device is preferable.

Further, examples of devices for performing the cleaning treatmentinclude a polishing device having a cleaning facility of, after thepolishing object after polishing has been removed from the polishingplaten, rubbing the polishing object with a cleaning brush. By the useof such a polishing device, the cleaning treatment of the polishingobject after polishing can be more efficiently performed.

As such a polishing device, a common polishing device having a holderfor holding the polishing object after polishing, a motor capable ofchanging the number of rotations, a cleaning brush, and the like isusable. As the polishing device, either a one-side polishing device or adouble-side polishing device may be used. In a case where the rinsepolishing step is performed after the CMP step, it is more efficient andpreferable that the cleaning treatment is performed using the samedevice as the polishing device used in the rinse polishing step.

The cleaning brush is not particularly limited and a resin brush ispreferably used. Materials for the resin brush are not particularlylimited and PVA (polyvinyl alcohol) is preferably used, for example. Asthe cleaning brush, a PVA sponge is particularly preferably used.

The cleaning conditions are also not particularly limited and can be setas appropriate according to the type of the cleaning object and the typeand the amount of the organic residues to be removed. For example, it ispreferable that the number of rotations of the cleaning brush is 10 rpmor more and 200 rpm or less, the number of rotations of the cleaningobject is 10 rpm or more and 100 rpm or less, and a pressure (polishingpressure) applied to the cleaning object is 0.5 psi or more and 10 psior less. A method for supplying the surface treatment composition to thecleaning brush is also not particularly limited and a method includingcontinuously supplying the surface treatment composition using a pump orthe like (in the one-way) is adopted, for example. The supply amount isnot limited and it is preferable that the surfaces of the cleaning brushand the cleaning object are constantly covered with the surfacetreatment composition and the supply amount is preferably 10 mL/min ormore and 5,000 mL/min or less. The cleaning time is also notparticularly limited and is preferably 5 seconds or more and 180 secondsor less in a step of using the surface treatment composition accordingto one aspect of the present invention. Within such a range, thecontaminants can be more effectively removed.

The temperature of the surface treatment composition in the cleaning isnot particularly limited and may be usually room temperature (25° C.)and may be increased to about 40° C. or more and 70° C. or less withinthe range where the performance is not impaired.

In the method (ii) above, the conditions of a cleaning method byimmersion are not particularly limited and known techniques can be used.

Before, after, or both before and after performing the cleaningtreatment by the method (i) or (ii), water cleaning may be performed.

It is preferable that the polishing object after polishing (cleaningobject) after cleaning is dried by removing water droplets adhering tothe surface using a spin dryer or the like. The surface of the cleaningobject may be dried by air-blow drying.

[Method for Producing Semiconductor Substrate]

The surface treatment method according to one aspect of the presentinvention can be suitably applied when the polishing object afterpolishing is a semiconductor substrate after polishing. Morespecifically, another aspect of the present invention further provides amethod for producing a semiconductor substrate in which the polishingobject after polishing is a semiconductor substrate after polishing andthe semiconductor substrate after polishing is surface-treated using theabove-described surface treatment composition.

Details of the semiconductor substrate to which such a production methodis applied are as described in the description of the polishing objectafter polishing to be surface-treated by the above-described surfacetreatment composition.

The method for producing a semiconductor substrate is not particularlylimited insofar as it includes a step of surface-treating the surface ofa semiconductor substrate after polishing using the surface treatmentcomposition according to one aspect of the present invention (surfacetreatment step). Examples of such a production method include, forexample, a method including a polishing step of forming a semiconductorsubstrate after polishing and a cleaning step. Another example of theproduction method includes a method including, in addition to thepolishing step and the cleaning step, a rinse polishing step between thepolishing step and the cleaning step. Hereinafter, each of these stepsis described.

<Polishing Step>

The polishing step which may be included in the method for producing asemiconductor substrate is a step of polishing a semiconductor substrateto form a semiconductor substrate after polishing.

The polishing step is not particularly limited insofar as it is a stepof polishing a semiconductor substrate and is preferably a chemicalmechanical polishing (CMP) step. The polishing step may be a polishingstep including a single step or may be a polishing step including aplurality of steps. Examples of the polishing step including a pluralityof steps include a step of performing a final polishing step after astock polishing step (rough polishing step), a step of performing onetime or two or more times of secondary polishing steps after primarypolishing step, and then performing a final polishing step, and thelike, for example. The surface treatment step using the surfacetreatment composition according to the present invention is preferablyperformed after the above-described final polishing step.

As the polishing composition, known polishing compositions can be usedas appropriate according to the properties of the semiconductorsubstrate. The polishing composition is not particularly limited andthose containing abrasives, acid salts, dispersion media, acids, and thelike can be preferably used, for example. Specific examples of such apolishing composition include a polishing composition containing ceria,polyacrylic acid, water, and maleic acid and the like.

As the polishing device, a common polishing device to which a holder forholding the polishing object, a motor capable of changing the number ofrotations, and the like are attached and which has a polishing platen towhich a polishing pad (polishing cloth) can be stuck is usable. As thepolishing device, either a one-side polishing device or a double-sidepolishing device may be used.

As the polishing pad, common nonwoven fabric, polyurethane, porousfluororesin, and the like can be used without being particularlylimited. The polishing pad is preferably subjected to grooving such thata polishing liquid is stored.

The polishing conditions are also not particularly limited. For example,the number of rotations of the polishing platen and the number ofrotations of a head (carrier) are preferably 10 rpm or more and 100 rpmor less. The pressure applied to the polishing object (polishingpressure) is preferably 0.5 psi or more and 10 psi or less. A method forsupplying the polishing composition to the polishing pad is also notparticularly limited and a method including continuously supplying thepolishing composition using a pump or the like (in the one-way) isadopted, for example. The supply amount is not limited and it ispreferable that the surface of the polishing pad is constantly coveredwith the polishing composition. The supply amount is preferably 10mL/min or more and 5,000 mL/min or less. The polishing time is also notparticularly limited and is preferably 5 seconds or more and 180 secondsor less in a step using the polishing composition.

<Surface Treatment Step>

The surface treatment step refers to a step of reducing the contaminantson the surface of the polishing object after polishing using the surfacetreatment composition according to the present invention. In the methodfor producing a semiconductor substrate, the cleaning step as thesurface treatment step may be performed after the rinse polishing stepor only the rinse polishing step or only the cleaning step may beperformed.

(Rinse Polishing Step)

In the method for producing a semiconductor substrate, the rinsepolishing step may be included between the polishing step and thecleaning step. The rinse polishing step is a step of reducing thecontaminants on the surface of the polishing object after polishing(semiconductor substrate after polishing) by the surface treatmentmethod (rinse polishing treatment method) according to one aspect of thepresent invention.

With respect to devices, such as the polishing device and the polishingpad, and the polishing conditions, the same devices and conditions asthose in the above-described polishing step are applicable exceptsupplying the surface treatment composition according to the presentinvention in place of supplying the polishing composition.

Details of a rinse polishing method used in the rinse polishing step areas described in the description concerning the rinse polishingtreatment.

(Cleaning Step)

In the method for producing a semiconductor substrate, the cleaning stepmay be included after the polishing step or may be included after therinse polishing step. The cleaning step is a step of reducing thecontaminants on the surface of the polishing object after polishing(semiconductor substrate after polishing) by the surface treatmentmethod (cleaning method) according to one aspect of the presentinvention.

Details of a cleaning method used in the cleaning step are as describedin the description concerning the cleaning method.

EXAMPLES

The present invention is described in more detail with reference toExamples and Comparative Examples described below. However, thetechnical scope of the present invention is not limited only to Examplesdescribed below. Unless otherwise specified, “%” and “part(s)” mean“mass %” and “mass part(s)”, respectively. Moreover, in Examplesdescribed below, unless otherwise specified, operations were performedunder the conditions of room temperature (25° C.)/Relative humidity RHof 40 to 50%.

As the weight average molecular weight of each high molecular weightcompound, a value of the weight average molecular weight (in terms ofpolyethylene glycol) measured by gel permeation chromatography (GPC) wasused. More specifically, the weight average molecular weight wasmeasured using the following devices under the following conditions.

GPC device: manufactured by Shimadzu Corporation

Model type: Prominence+ELSD detector (ELSD-LTII)

Column: VP-ODS (manufactured by Shimadzu Corporation)

Mobile phase A: MeOH

-   -   B: 1% Aqueous acetic acid solution

Flow rate: 1 mL/min

Detector: ELSD temp. 40° C., Gain 8, N2GAS 350 kPa

Oven temperature: 40° C.

Injection amount: 40 μL

<Preparation of Surface Treatment Composition>

Example 1: Preparation of Surface Treatment Composition (A-1)

0.1 mass part of poly-N-vinylacetamide (Weight average molecular weight(Mw): 300,000; Constituent unit represented by Formula (1): 100 mol %)and 0.01 mass part of a polystyrene sulfonate-acrylic acid copolymer(Weight average molecular weight (Mw): 10,000) as the ionic dispersantwere individually mixed with water (deionized water) when the totalamount of a composition was 100 mass parts, and then nitric acid as a pHadjuster was added in an amount that sets the pH to 2.5 to prepare asurface treatment composition (A-1). The pH of the surface treatmentcomposition (A-1) (Liquid temperature: 25° C.) was measured with a pHmeter (Manufactured by HORIBA, LTD., Product Name: LAQUA (RegisteredTrademark)).

Examples 2 to 22 and Comparative Examples 1 to 7: Preparation of SurfaceTreatment Compositions (A-2) to (A-22) and (a-1) to (a-7)

Surface treatment compositions were prepared by the same operation as inExample 1 except using components of types, molecular weights, andcontents illustrated in Table 1 and adjusting the pH of each surfacetreatment composition to a pH illustrated in Table 1 (using ammoniawater when making the surface treatment composition neutral oralkaline). In Table 1, “-” indicates that the component was not used. InTable 1, “vinyl polymer” refers to one obtained by homopolymerizing orcopolymerizing a vinyl monomer.

In Table 1, PSS-PA indicates “polystyrene sulfonate-acrylic acidcopolymer”.

<Evaluation>

<Preparation of Polishing Object after Polishing (Surface TreatmentObject)>

A silicon nitride substrate after polishing, a TEOS substrate afterpolishing, and a polysilicon substrate after polishing which werepolished by a chemical mechanical polishing (CMP) step described lateror a silicon nitride substrate after polishing, a TEOS substrate afterpolishing, and a polysilicon substrate after polishing which werefurther treated by a rinse step described later as necessary wereprepared as surface treatment objects.

[CMP Step]

The silicon nitride substrate, the TEOS substrate, and the polysiliconsubstrate which are semiconductor substrates were polished using 1 mass% of a polishing composition M (Composition; ceria, Primary particlediameter of 60 nm, Secondary particle diameter of 100 nm), 0.18 mass %of a maleic acid aqueous solution having a concentration of 30 mass %,0.25 mass % of polyacrylic acid (Molecular weight: 6,000), and water asa solvent under the following conditions. Herein, 300 mm wafers wereused for the silicon nitride substrate, the TEOS substrate, and thepolysilicon substrate.

(Polishing Device and Polishing Conditions)

Polishing device: FREX 300E manufactured by Ebara Corporation

Polishing pad: Soft pad H800 manufactured by FUJIBO HOLDINGS, INC.

Polishing pressure: 2.0 psi (1 psi=6894.76 Pa, which similarly appliesto the following description)

Number of rotations of polishing platen: 90 rpm

Number of rotations of head: 90 rpm

Supply of polishing composition: One-way

Supply amount of polishing composition: 200 mL/min.

Polishing time: For 60 seconds

[Rinse Polishing Treatment Step]

With respect to the silicon nitride substrate after polishing, the TEOSsubstrate after polishing, and the polysilicon substrate after polishingwhich were polished by the CMP step, each substrate after polishing wasremoved from the polishing platen. Subsequently, each substrate afterpolishing was attached onto another polishing platen, and then rinsepolishing treatment was performed to each substrate surface using eachof the surface treatment compositions prepared above under the followingconditions within the same polishing device.

(Polishing Device and Polishing Conditions)

Polishing device: FREX 300E manufactured by Ebara Corporation

Polishing pad: Soft pad H800 manufactured by FUJIBO HOLDINGS, INC.

Polishing pressure: 1.0 psi (1 psi=6894.76 Pa, which similarly appliesto the following description)

Number of rotations of polishing platen: 60 rpm

Number of rotations of head: 60 rpm

Supply of polishing composition: One-way

Supply amount of polishing composition: 300 mL/min.

Polishing time: For 60 seconds

(Water Cleaning Step)

Each substrate after the rinse polishing treatment obtained above wascleaned for 60 seconds while pouring deionized water (DIW) using a PVAbrush after the rinse polishing in a cleaning unit. Thereafter, eachsubstrate was dried with a spin dryer for 30 seconds.

<Evaluation>

Each substrate after the water cleaning step obtained above was measuredand evaluated for the following items. The evaluation results areillustrated in Table 2.

[Measurement of Total Number of Defects]

The number of defects of each of the silicon nitride substrate (0.038 mor more), the TEOS substrate (0.037 μm or more), and the polysiliconsubstrate (0.057 μm or more) after the surface treatment after the watercleaning step obtained above was measured. For the measurement of thenumber of defects, a wafer defect tester SP-5 manufactured by KLA TENCORwas used. The measurement was performed for a remaining portionexcluding a 3 mm wide portion (portion with a width from 0 mm to 3 mmwhen an outer peripheral end portion was set to 0 mm) from the outerperipheral end portion of each substrate surface after the surfacetreatment.

[Evaluation of Number of Organic Residues]

The polishing objects after polishing after subjected to the surfacetreatment were measured for the number of organic residues using aReview SEM RS6000 manufactured by Hitachi, Ltd. by SEM observation.First, 100 defects present on the remaining portion excluding the 3 mmwide portion from the outer peripheral end portion of one side of thepolishing object after polishing were sampled by SEM observation.Subsequently, the organic residues were visually distinguished by SEMobservation out of the sampled 100 defects, and then the number of theorganic residues was confirmed, whereby the ratio (%) of the organicresidues in the defects was calculated. Then, the product of the totalnumber (pieces) of defects of the silicon nitride substrate (0.038 μm ormore), the TEOS substrate (0.037 μm or more), and the polysiliconsubstrate (0.057 μm or more) measured using the SP-5 manufactured by KLATENCOR in the evaluation of the total number of defects described aboveand the ratio (%) of the organic residues in the defects calculated fromthe above-described SEM observation result was calculated as the number(pieces) of the organic residues.

The ratio (%) of the organic residues in the defects was set to 10% inthe silicon nitride (SiN) substrate, 10% in the TEOS substrate, and 90%in the polysilicon substrate. As the criteria for determining that thenumber of the organic residues was reduced, cases where the number ofthe organic residues was 1,500 or less in the TEOS substrate and thenumber of the organic residues was 5,000 or less in the polysiliconsubstrate were determined to be good.

With respect to each surface treatment composition, the evaluationresults of the organic residues when using the silicon nitride substrateafter polishing, when using the TEOS substrate after polishing, and whenusing the polysilicon substrate after polishing as the surface treatmentobject are illustrated in Table 2 below.

TABLE 1 Vinyl polymer Ionic dispersant Glycerol-based water-solublepolymer Content Content Content Type Mw (wt %) Type Mw (wt %) Type Mw(wt %) pH Ex. 1 (A-1) Poly-N-vinylacetamide 300,000 0.1 PSS-PA 10,0000.01 — — — 2.5 Ex. 2 (A-2) Poly-N-vinylacetamide 300,000 0.1 — — — — — —2.5 Ex. 3 (A-3) Poly-N-vinylacetamide 300,000 0.1 PSS-PA 10,000 0.01Polyglycerol 15,000 0.1 2.5 Ex. 4 (A-4) Poly-N-vinylacetamide 50,0000.075 PSS-PA 10,000 0.01 — — — 2.5 Ex. 5 (A-5) Poly-N-vinylacetamide50,000 0.1 PSS-PA 10,000 0.01 — — — 2.5 Ex. 6 (A-6)Poly-N-vinylacetamide 50,000 0.2 PSS-PA 10,000 0.01 — — — 2.5 Ex. 7(A-7) Poly-N-vinylacetamide 50,000 0.3 PSS-PA 10,000 0.01 — — — 2.5 Ex.8 (A-8) Poly-N-vinylacetamide 100,000 0.1 PSS-PA 10,000 0.01 — — — 2.5Ex. 9 (A-9) Poly-N-vinylacetamide 900,000 0.1 PSS-PA 10,000 0.01 — — —2.5 Ex. 10 (A-10) Poly-N-vinylacetamide 50,000 0.1 PSS-PA 10,000 0.01 —— — 2.0 Ex. 11 (A-11) Poly-N-vinylacetamide 50,000 0.1 PSS-PA 10,0000.01 — — — 3.0 Ex. 12 (A-12) Poly-N-vinylacetamide 50,000 0.1 PSS-PA10,000 0.01 — — — 4.0 Ex. 13 (A-13) Poly-N-vinylacetamide 50,000 0.1PSS-PA 10,000 0.01 — — — 5.0 Ex. 14 (A-14) Poly-N-vinylacetamide 50,0000.1 PSS-PA 10,000 0.01 — — — 6.0 Ex. 15 (A-15) Poly-N-vinylacetamide50,000 0.1 PSS-PA 10,000 0.01 — — — 7.0 Ex. 16 (A-16)Poly-N-vinylacetamide 50,000 0.1 PSS-PA 10,000 0.01 — — — 8.0 Ex. 17(A-17) Poly-N-vinylacetamide 50,000 0.1 PSS-PA 10,000 0.01 — — — 9.0 Ex.18 (A-18) Poly-N-vinylacetamide 50,000 0.1 PSS-PA 10,000 0.01 — — — 10.0Ex. 19 (A-19) Poly-N-vinylacetamide 300,000 0.1 PSS-PA 10,000 0.01 — — —4.0 Ex. 20 (A-20) Poly-N-vinylacetamide 300,000 0.1 PSS-PA 10,000 0.01 —— — 6.0 Ex. 21 (A-21) Poly-N-vinylacetamide 300,000 0.1 PSS-PA 10,0000.01 — — — 8.0 Ex. 22 (A-22) Poly-N-vinylacetamide 300,000 0.1 PSS-PA10,000 0.01 — — — 12.0 Comp. Ex. 1 (a-1) PVA 10,000 0.1 — — — — — — 2.5Comp. Ex. 2 (a-2) PVA 10,000 0.1 PSS-PA 10,000 0.01 — — — 2.5 Comp. Ex.3 (a-3) PVA 10,000 0.1 — — — Polyglycerol 15,000 0.1 2.5 Comp. Ex. 4(a-4) PVA 10,000 0.1 PSS-PA 10,000 0.01 Polyglycerol 15,000 0.1 2.5Comp. Ex. 5 (a-5) PVA 5,000 0.1 — — — — — — 2.5 Comp. Ex. 6 (a-6) PVA80,000 0.1 — — — — — — 2.5 Comp. Ex. 7 (a-7) PVA 100,000 0.1 — — — — — —2.5

TABLE 2 Total number of defects (pieces) Organic residues (pieces) SP-5SP-5 SiN TEOS PolySi Total number Total number Total number ≥0.038 μm≥0.037 μm ≥0.057 μm of defects 10% of defects 10% of defects 90% Ex. 1(A-1) 1,312 11,782 1,849 131 1,178 1,664 Ex. 2 (A-2) 250,000 10,7551,988 25,000 1,076 1,789 Ex. 3 (A-3) 2,019 10,660 1,051 202 1,066 946Ex. 4 (A-4) 2,629 7,343 3,645 263 734 3,281 Ex. 5 (A-5) 2,022 8,1983,959 202 820 3,563 Ex. 6 (A-6) 3,004 8,052 2,889 300 805 2,600 Ex. 7(A-7) 2,894 7,419 3,409 289 742 3068 Ex. 8 (A-8) 2,611 11,943 1,662 2611,194 1,496 Ex. 9 (A-9) 2,832 14,501 1,376 283 1,450 1,238 Ex. 10 (A-10)1,988 7,486 3,299 199 749 2,969 Ex. 11 (A-11) 2,114 6,697 2,901 211 6702,611 Ex. 12 (A-12) 5,677 7,534 2,379 568 753 2,141 Ex. 13 (A-13)250,000 7,679 2,476 25,000 768 2,228 Ex. 14 (A-14) 250,000 8,639 2,87325,000 864 2,586 Ex. 15 (A-15) 250,000 8,491 2,697 25,000 849 2,427 Ex.16 (A-16) 250,000 8,994 2,569 25,000 899 2,312 Ex. 17 (A-17) 250,0008,120 2,863 25,000 812 2,577 Ex. 18 (A-18) 250,000 6,329 1,994 25,000633 1,795 Ex. 19 (A-19) 4,492 12,085 1,553 449 1,209 1,398 Ex. 20 (A-20)250,000 14,435 1,962 25,000 1,444 1,766 Ex. 21 (A-21) 250,000 10,9831,093 25,000 1,098 984 Ex. 22 (A-22) 250,000 11,689 832 25,000 1,169 749Comp. Ex. 1 (a-1) 250,000 28,264 13,540 25,000 2,826 12,186 Comp. Ex. 2(a-2) 2,245 27,318 11,755 225 2,732 10,580 Comp. Ex. 3 (a-3) 250,00028,632 10,413 25,000 2,863 9,372 Comp. Ex. 4 (a-4) 3,066 26,542 9,978307 2,654 8,980 Comp. Ex. 5 (a-5) 250,000 23,301 15,022 25,000 2,33013,520 Comp. Ex. 6 (a-6) 250,000 26,499 11,245 25,000 2,650 10,121 Comp.Ex. 7 (a-7) 250,000 30,020 10,771 25,000 3,002 9,694

As is clear from Table 1 and Table 2 above, it was found that thesurface treatment compositions of Examples can reduce the organicresidues on the surfaces of the polishing objects after polishingcompared to the surface treatment compositions of Comparative Examples.

Specifically, it was found that the surface treatment compositions ofExamples 1 to 22 containing poly-N-vinylacetamide can reduce the organicresidues on the surface of the TEOS substrate after polishing comparedto the surface treatment compositions of Comparative Examples 1 to 7.

Further, it was found that the surface treatment compositions ofExamples 1 to 22 in which the weight average molecular weight (Mw) ofpoly-N-vinylacetamide is 50,000 or more and 900,000 or less can reduceboth the organic residues on the surface of the TEOS substrate afterpolishing and the organic residues on the surface of the polysiliconsubstrate after polishing compared to Comparative Examples 1 to 7.

Further, it was found that the surface treatment compositions ofExamples 1 to 11 containing at least one of the glycerol-basedwater-soluble polymer and the ionic polymer and having a pH of 3.0 orless can reduce both the organic residues on the surface of the TEOSsubstrate after polishing and the organic residues on the surface of thesilicon nitride substrate after polishing compared to ComparativeExamples 1 to 7.

What is claimed is:
 1. A surface treatment composition comprising: apolymer having a constituent unit represented by Formula (1) below; anionic dispersant; and water, the surface treatment composition beingused for treating a surface of a polishing object after polishing,

wherein, in Formula (1) above, R¹ is a hydrocarbon group having 1 to 5carbon atoms and R² is a hydrogen atom or a hydrocarbon group having 1to 3 carbon atoms.
 2. The surface treatment composition according toclaim 1, wherein a pH is 5 or less.
 3. The surface treatment compositionaccording to claim 1, wherein a pH is 3 or less.
 4. The surfacetreatment composition according to claim 1 further comprising: awater-soluble polymer having a constituent unit derived from glycerol.5. The surface treatment composition according to claim 1, wherein theionic dispersant is a high molecular weight compound having a sulfonicacid (salt) group.
 6. The surface treatment composition according toclaim 1, wherein the surface treatment composition is substantially freefrom an abrasive.
 7. The surface treatment composition according toclaim 1, wherein the polishing object after polishing containspolysilicon.
 8. The surface treatment composition according to claim 1,wherein a weight average molecular weight of the polymer is 50,000 ormore and 900,000 or less.
 9. A method for producing a surface treatmentcomposition comprising: mixing a polymer having a constituent unitrepresented by Formula (1) below, an ionic dispersant, and water,

wherein, in Formula (1) above, R¹ is a hydrocarbon group having 1 to 5carbon atoms and R² is a hydrogen atom or a hydrocarbon group having 1to 3 carbon atoms.
 10. A surface treatment method comprising:surface-treating a polishing object after polishing using the surfacetreatment composition according to claim 1 to reduce an organic residueon a surface of the polishing object after polishing.
 11. The surfacetreatment method according to claim 10, wherein the surface treatmentincludes rinse polishing or cleaning.
 12. A method for producing asemiconductor substrate comprising: a surface treatment step of reducingan organic residue on a surface of a polishing object after polishing bythe surface treatment method according to claim 10, wherein thepolishing object after polishing is a semiconductor substrate afterpolishing.
 13. The surface treatment composition according to claim 2,wherein a pH is 3 or less.
 14. The surface treatment compositionaccording to claim 2 further comprising: a water-soluble polymer havinga constituent unit derived from glycerol.
 15. The surface treatmentcomposition according to claim 3 further comprising: a water-solublepolymer having a constituent unit derived from glycerol.
 16. The surfacetreatment composition according to claim 2, wherein the surfacetreatment composition is substantially free from an abrasive.